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traviscross merged 1 commit into from
Dec 17, 2025
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Unwrap const_eval.md #2112

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27 changes: 7 additions & 20 deletions src/const_eval.md
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Expand Up @@ -2,16 +2,13 @@ r[const-eval]
# Constant evaluation

r[const-eval.general]
Constant evaluation is the process of computing the result of
[expressions] during compilation. Only a subset of all expressions
can be evaluated at compile-time.
Constant evaluation is the process of computing the result of [expressions] during compilation. Only a subset of all expressions can be evaluated at compile-time.

r[const-eval.const-expr]
## Constant expressions

r[const-eval.const-expr.general]
Certain forms of expressions, called constant expressions, can be evaluated at
compile time.
Certain forms of expressions, called constant expressions, can be evaluated at compile time.

r[const-eval.const-expr.const-context]
Expressions in a [const context] must be constant expressions.
Expand All @@ -23,14 +20,10 @@ r[const-eval.const-expr.runtime-context]
Outside of const contexts, constant expressions *may* be, but are not guaranteed to be, evaluated at compile time.

r[const-eval.const-expr.error]
Behaviors such as out of bounds [array indexing] or [overflow] are compiler errors if the value
must be evaluated at compile time (i.e. in const contexts). Otherwise, these
behaviors are warnings, but will likely panic at run-time.
Behaviors such as out of bounds [array indexing] or [overflow] are compiler errors if the value must be evaluated at compile time (i.e. in const contexts). Otherwise, these behaviors are warnings, but will likely panic at run-time.

r[const-eval.const-expr.list]
The following expressions are constant expressions, so long as any operands are
also constant expressions and do not cause any [`Drop::drop`][destructors] calls
to be run.
The following expressions are constant expressions, so long as any operands are also constant expressions and do not cause any [`Drop::drop`][destructors] calls to be run.

r[const-eval.const-expr.literal]
* [Literals].
Expand All @@ -39,8 +32,7 @@ r[const-eval.const-expr.parameter]
* [Const parameters].

r[const-eval.const-expr.path-item]
* [Paths] to [functions] and [constants].
Recursively defining constants is not allowed.
* [Paths] to [functions] and [constants]. Recursively defining constants is not allowed.

r[const-eval.const-expr.path-static]
* Paths to [statics] with these restrictions:
Expand Down Expand Up @@ -79,8 +71,7 @@ r[const-eval.const-expr.closure]
* [Closure expressions] which don't capture variables from the environment.

r[const-eval.const-expr.builtin-arith-logic]
* Built-in [negation], [arithmetic], [logical], [comparison] or [lazy boolean]
operators used on integer and floating point types, `bool`, and `char`.
* Built-in [negation], [arithmetic], [logical], [comparison] or [lazy boolean] operators used on integer and floating point types, `bool`, and `char`.

r[const-eval.const-expr.borrows]
* All forms of [borrow]s, including raw borrows, except borrows of expressions whose temporary scopes would be extended (see [temporary lifetime extension]) to the end of the program and which are either:
Expand Down Expand Up @@ -267,11 +258,7 @@ r[const-eval.const-context.block]
* A [const block]

r[const-eval.const-context.outer-generics]
Const contexts that are used as parts of types (array type and repeat length
expressions as well as const generic arguments) can only make restricted use of
surrounding generic parameters: such an expression must either be a single bare
const generic parameter, or an arbitrary expression not making use of any
generics.
Const contexts that are used as parts of types (array type and repeat length expressions as well as const generic arguments) can only make restricted use of surrounding generic parameters: such an expression must either be a single bare const generic parameter, or an arbitrary expression not making use of any generics.

r[const-eval.const-fn]
## Const functions
Expand Down